Isolation of a flax pectin methylesterase promoter and its expression in transgenic tobacco

Pectin methylesterases (PME) catalyze the de-esterification of methoxylated pectins in plant cell walls. We have isolated a 1.9 kb regulatory region u pstream from the Lupme3 coding sequence of Linum usitatissimum L. (flax) us ing a 'Polymerase Chain Reaction (PCR) walking' strategy. Two 5 ' truncated deletion fragments (1.5 and 0.44 kb) of this potential promoter sequence w ere inserted upstream of the gus reporter gene in order to study their expr ession in transgenic plants. These constructs were transferred into Nicotia na tabacum, a heterologous system using Agrobacterium tumefaciens. Expressi on of the reporter gene was analyzed in regenerated transgenic plants and c alli to study the promoter activities of these sequences. This expression w as observed in calli with both constructs. In contrast, expression in organ s was only detected in tobacco plants transformed with the largest (1.5 kb) construct. This long fragment triggered expression in roots and immature o r vitrified leaves. Expression in both organs was localized in the vasculat ure, but also detected in the root meristem. These results are the first ev idence, to our knowledge, of the spatial and temporal regulation of a speci fic pme promoter of flax. Localization of Lupme3 promoter activity in vascu lar tissues of immature organs provides an insight into the role of this PM E isoform in cell elongation and differentiation. (C) 2001 Elsevier Science Ireland Ltd. All rights reserved.